Analysis of biological and structural factors implicated in the clinical success of orthodontic miniscrews at posterior maxillary interradicular sites.

OBJECTIVE: This study aims to evaluate success factors implicated in clinical orthodontic miniscrew stability after their interradicular placement in maxilla. MATERIALS AND METHODS: Six hundred seventy-six miniscrews were inserted in maxillary interradicular sites in a sample of 276 patients (109 males and 167 females; mean age 19 ± 1.7 years) and immediately loaded. Percentage failure rate was recorded, and the influence of the following factors was investigated: structural (miniscrew length, diameter and body shape), operative (side of insertion site, pilot hole drilling or not) and biological (maximal insertion torque [MIT] and type of gingiva). A chi-square test with Monte Carlo correction was performed to detect the influence of these variables on the failure rate of orthodontic miniscrews. Then both multivariate logistic regression and post hoc analysis were performed, followed by classification and regression tree (CART) analysis. RESULTS: The average success rate was 88%. The principal factors implicated in the failure rate were miniscrew length, MIT values and type of gingiva. Specifically, 8 mm miniscrew length, alveolar mucosa and 5-10 Ncm MIT values were linked to higher failure rates. According to CART, the main variable influencing failure is miniscrew length (≤ 8 mm for higher failure rates). For others, MIT values of 5-10 Ncm are linked to higher failure rates (p < 0.05). CONCLUSION: Orthodontic miniscrews inserted in the maxilla display good success rates. However, clinicians should be discouraged from using miniscrews of length ≤ 8 mm and MIT values < 10 Ncm, even with longer miniscrews. CLINICAL RELEVANCE: Information about factors related to failure rate of miniscrews placed at posterior maxillary interradicular sites is given.

Temporomandibular disorders and dental occlusion. A systematic review of association studies: end of an era?

To answer a clinical research question: 'is there any association between features of dental occlusion and temporomandibular disorders (TMD)?' A systematic literature review was performed. Inclusion was based on: (i) the type of study, viz., clinical studies on adults assessing the association between TMD (e.g., signs, symptoms, specific diagnoses) and features of dental occlusion by means of single or multiple variable analysis, and (ii) their internal validity, viz., use of clinical assessment approaches to TMD diagnosis. The search accounted for 25 papers included in the review, 10 of which with multiple variable analysis. Quality assessment showed some possible shortcomings, mainly related with the unspecified representativeness of study populations. Seventeen (N = 17) articles compared TMD patients with non-TMD individuals, whilst eight papers compared the features of dental occlusion in individuals with TMD signs/symptoms and healthy subjects in non-patient populations. Findings are quite consistent towards a lack of clinically relevant association between TMD and dental occlusion. Only two (i.e., centric relation [CR]-maximum intercuspation [MI] slide and mediotrusive interferences) of the almost forty occlusion features evaluated in the various studies were associated with TMD in the majority (e.g., at least 50%) of single variable analyses in patient populations. Only mediotrusive interferences are associated with TMD in the majority of multiple variable analyses. Such association does not imply a causal relationship and may even have opposite implications than commonly believed (i.e., interferences being the result, and not the cause, of TMD). Findings support the absence of a disease-specific association. Based on that, there seems to lack ground to further hypothesise a role for dental occlusion in the pathophysiology of TMD. Clinicians are encouraged to abandon the old gnathological paradigm in TMD practice.

Phonetic analysis during treatment with rapid maxillary expander.

OBJECTIVES: To investigate possible changes and/or device-related impairments in phonetic habits produced by rapid maxillary expansion (RME). MATERIALS AND METHODS: Thirty-five patients scheduled for RME were divided into two groups: Group A (banded two-arm Hyrax) and Group B (banded four-arm Hyrax). Speech samples were collected at six time points, before, during and after RME removal. Acoustical analysis was performed using PRAAT and BioVoice analysis tools. Ten volunteers completed a questionnaire on the acceptability of patient's speech. Maxillary dimensions and palatal volume were measured on dental casts before and after expansion using a digital gauge. RESULTS: Voice analysis showed an increase in the peak frequency of fricative consonants (/s/,/ʃ/) after expansion, whereas there was no change of formant frequencies of palatal consonants (/ɲ/,/ʎ/). Vowel /i/ displayed a lowering of the first formant frequency, and an increase in the second and third formant frequencies. After bonding, Group B showed both a greater reduction in the peak frequency of fricatives and a greater increase in the formant frequencies of palatal consonants than Group A. CONCLUSION: Rapid maxillary expansion causes a slight phonetic change in the acoustical parameters of both consonants and vowels. The two-arm Hyrax caused less speech impairment than the four-arm Hyrax during the treatment.

Unexpected artefacts and occult pathologies under CBCT.

PURPOSE: To present the most frequent occult pathologies unexpectedly encountered via cone-beam computed tomography (CBCT), with particular reference to the diagnostic role of the dentist and that of the radiographer, with a view to clarifying where the diagnostic responsibility lies. MATERIAL AND METHODS: A narrative literature review on the most diffused occult pathologies under CBCT was conducted, with iconographical guide as an example for each category. RESULTS: The most frequent forms of unexpected pathologies encountered are: the presence of foreign bodies, airway anomaly, and the presence of radio-opacity or -transparency in the maxillofacial district. CONCLUSIONS: The orthodontists must know that they are responsible to recognize these frequent, and potentially serious, pathologies of the head and neck. If the dentist feels unable to take on this responsibility, he or she should, however, be sure to have the scans read by a specialist radiologist.

Correlation between coronal and apical arch form and degree of divergence: a volumetric computed tomography analysis.

PURPOSE: To determine the existence of any correlation between the degree of divergence and apical and coronal arch form using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: A total of 176 (88 coronal and 88 apical) CBCT scans pertaining to a sample of 44 subjects (16 males and 28 females), of which 26 were Class I, 14 Class II and 4 Class III, were analysed. A lateral projection of the skull was obtained from each VCT and cephalometric tracing was performed (according to Ricketts) so as to divide the sample into subgroups based on the degree of divergence (11 short-faced, 18 norm-faced and 15 long-faced subjects). Dahlberg's index values were calculated and Student's t-test for paired data was applied. RESULTS: On the whole, the hyperbolic cosine curve was found to be the most representative of the arch forms considered. CONCLUSIONS: A correlation between degree of divergence and the arch form of the apical and, especially, coronal portions of both the upper and lower jaws was revealed.

Quantitive evaluation of dentin sialoprotein (DSP) using microbeads - a potential early marker of root resorption.

PURPOSE: This study had the aim of comparing two different methods of analysing dentin sialoprotein (DSP) in the gingival crevicular fluid (GCF): the conventional eLISA approach and a new method involving the use of magnetic micro-beads coated with an antibody specific for DSP prior to eLISA analysis. MATERIALS AND METHODS: GCF was taken from six patients following twelve weeks of orthodontic treatment using paper strips inserted into the mesial and distal sulci of the upper incisors, and analysed using both methods. RESULTS: Statistical analysis of the results using the Mann-Whitney non-parametric test showed that the micro-bead approach conferred more reliability and less variability on the conventional eLISA approach. Furthermore, this method, for the first time, enables the quantification of the DSP in the sample in ng/µl. CONCLUSIONS: The innovative micro-bead/eLISA approach proposed provides a reliable means of quantifying the DSP in the GCF.

Orthofile®: a new approach for mechanical interproximal reduction : a scanning electron microscopic enamel evaluation.

PURPOSE: The aim of this in vitro study was to evaluate the stripping achieved on different teeth (incisors, canines, and premolars) by two grades of abrasive strips used for the first and tenth time. Our second aim was to test the efficacy of these strips by calculating the time necessary to perform interproximal reductions of 0.10, 0.20, and 0.30 mm. METHODS: Four models were constructed using extracted teeth affixed in wax. The upper and lower arches were set on plaster bases and fixed in wax, carefully creating contact points. All model mouths were treated with artificial saliva (Oral Balance®) in order to simulate the biological conditions in the oral cavity. We then tested specific air-rotor strips of different grades and degrees of wear (15-µm-grain and 25-µm-grain Orthofile® strips). Afterwards the teeth from all samples were cut lengthwise in half, and each mesial and distal portion was gold-plated and observed under SEM at incremental magnification (30, 60, and 100 µm). RESULTS: The 25-µm-grain strip was more effective than the 15-µm-grain strip, irrespective of the tooth involved. Second, the finishing phase with specific polishing strips after interproximal reduction was fundamental in reducing the number of abrasions and irregularities created by stripping, in particular after using the 25-µm-grain strip. To achieve the best result, the entire abraded area must be polished. CONCLUSION: This system permits a rapid and effective stripping procedure in direct proportion to the strip's grain and in inverse proportion to the wear from its use. Further research will enable us to compare this system with similar procedures.

Treatment of the noncompliant Class III growing patient.

The treatment of skeletal Class III malocclusion is one of the most challenging problems that confronts the practicing orthodontist, particularly in the late deciduous or early mixed dentition periods. In addition to its inherent difficulty, compromised results can also be due to poor patient cooperation; orthopaedic appliances for Class III treatment can be uncomfortable and unaesthetic. There are few acceptable alternatives when a patient refuses to wear an orthopaedic appliance. The aim of this report is to introduce an approach for the treatment of the non compliant dental and skeletal Class III in growing patients. The Smart Wire (SW) is a new orthodontic device simply formed by a 1 mm diameter stainless-steel arch wire that is inserted into the extraoral tube of the upper molar bands. The SW interferes with lower incisors in the front upon mandibular closure. Thus, a distally directed force is applied on the lower incisors and on the mandible while at the same time a mesial force is transmitted onto the upper molars. This combination of force and reaction guides the orthodontic-orthopaedic correction of Class III malocclusions in growing patients.

Histomorphometric study of bone reactions during orthodontic tooth movement in rats.

The biological response to orthodontic tooth movement has generally focused on reactions within the periodontal ligament (PDL), whereas less attention has been paid to the behavior of neighboring bone. The purpose of the study was to describe the influence of orthodontic force on bone surrounding the displaced tooth and the adjacent, untreated teeth. Bone changes in relation to treatment time and different sites were investigated. A mesial tipping of the left maxillary first molar was obtained from 54 adult male Wistar rats. Oxytetracycline was injected subcutaneously 48 h before killing, which took place after 4, 7, or 14 days. The maxilla was fixed in paraformaldehyde and embedded undecalcified in methylmethacrylate. A set of thick horizontal sections was taken from the cervical, intermediate, and apical levels of the roots. The sections were microradiographed and analyzed microscopically under bright-field and fluorescent illumination. Bone fraction and PDL width was measured using a Zeiss Videoplan device equipped with an overlay system. New bone formation was detected by oxytetracycline labels. The analysis showed a consistent, significant decrease of the alveolar bone fraction around both displaced and adjacent teeth at all treatment times. Apposition, indicated by the tetracycline uptake, was found on the periosteal side of the treated hemimaxilla and, after 14 days, also on the surface toward which the tooth was moving and around the adjacent teeth. These results suggest that a time rather than a space relationship exists between bone resorption and formation and that the whole hemimaxilla reacts to the mechanical challenge, resembling the regional acceleratory phenomenon (RAP) observed in other circumstances.

The lingual distalizer system.

Class II molar relationships can be corrected by several methods. In previous systems, orthodontic forces have been applied to crowns and distal movement of the first molar has mainly been by tipping and a rotation of the crowns. A new Lingual Distalizer (LD) has recently been developed to distalize the maxillary molars without the drawbacks of previous appliances. The lingual distalizer is relatively easy to insert, is well-tolerated, does not require patient co-operation and is aesthetic. It distalizes molars without loss of anchorage and moves them with bodily translation.

Effects of continuous and intermittent forces on human fibroblasts in vitro.

Orthodontics is based upon the cellular response to biomechanical forces. However, little is known about the way cells respond to such forces. An experimental model has been designed to study the morphological and metabolic behaviour of human cells, subjected to cyclical or static mechanical loads. The model involves attaching human fibroblasts to silicone collagen-coated membranes, which are subjected to either continuous of cyclical stretching by a motor coupled with a movable supporting frame. The effect of continuous or cyclical stretching on the secretion of collagenase, an enzyme thought to play an important role in the process of tooth movement, was measured. Cyclical stretching of fibroblasts over a 4-day period, approximately doubled collagenase production as compared with the control. Continuous stretching, on the other hand, was only 50 per cent as effective in enhancing enzyme release. In contrast, the secretion of the collagenase inhibitor was unaffected by either form of mechanical deformation. To understand the effect of cyclical forces further, a morphological study using humane fibroblasts was performed. It was found that stretching or compression delivered an immediate and proportional deformation of the cells. After 10-15 minutes the morphology of cells readapted to the new mechanical environment, causing a loss of the biological activation. This suggest that a new mechanical stimulus is necessary to induce a new biological reaction.

[Functional anterior limits of the dentition. 2]. / Considerazioni sul limite anteriore funzionale della dentatura--Parte II.

The Authors search in the most used cephalometric techniques the values defining superior incisor position relationship with cephalometric planes. They assess cephalometric values on 50 functionally stable patients at the end of treatment with axiographic method.

[Electromyographic response to progressive activation of functional appliances]. / Risposta elettromiografica alla attivazione progressiva delle apparecchiature funzionali.

The Authors, according to the literature, carried out an electromyographic study on young Class II patients. Muscolar activity was studied during rest and with Frankel's functional regulator in different conditions of activation. Analysis of obtained results supports the author's idea of an individual activation of the functional appliances.

[New software for a prevention program in orodental pathology]. / Proposta di un nuovo software per un programma di prevenzione delle patologie oro-dentali.

The Authors describe a new software planned to manage the data of a community caries preventing program. The rationale and the applications of the software are described.

[Biomechanical and physical characteristics of horizontally loaded lingual brackets]. / Caratteristiche biomeccaniche e fisiche dell'attacco linguale a caricamento orizzontale.

The Authors assess, by SEM analysis, biomechanical and physical characteristics of lingual orthodontic appliances of Ormco CO. Each part of the bracket structure has been observed and assessed.

[Statistical cephalometric study of the anterior cranial base]. / Studio statistico cefalometrico sulla base cranica anteriore.

The Authors have carried out a cephalometric and statistic study, running at right angles, searching for a reference parameter regarding the S.N. length (skulled front base) so that it can be used in the differential diagnosis of the skeleton Classes.